Therya_notes_175

THERYA NOTES 2024, Vol. 5 : 216-222 DOI: 10.12933/therya_notes-24-175 ISSN 2954-3614

New sightings of southern elephant seals (Mirounga leonina) in México: Citizen science and wildlife dispersion

Nuevos avistamientos de elefantes marinos del sur (Mirounga leonina) en México: Ciencia ciudadana y dispersión de vida silvestre

Isai David Barba-Acuña1*, Juan Pablo Gallo-Reynoso1, José Ángel Ortega-Borchardt1, Manuel Muñoz-Espinoza2, Claudia J. Hernández-Camacho3, Elena B. Eder4, Lynda Dobbin-Turner5, and Christian Casillas-Angón6

1Centro de Investigación en Alimentación y Desarrollo, A. C. Unidad Guaymas. Carretera al Varadero Nacional km 6.6, C. P. 85480, Guaymas. Sonora, México. E-mail: isai.barba@ciad.mx (IDB-A); jpgallo@ciad.mx (JPG-R); jangelortegab@gmail.com (JÁO-B).

2Grupo Lobos. Ejido Rodolfo Campodónico, H. Caborca. Sonora, México. E-mail: munozespinozamanuel77@gmail.com (MM-E).

3Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional. Playa Palo de Santa Rita, C. P. 23096, La Paz. Baja California Sur, México. E-mail: jcamacho@ipn.mx (CJH-C).

4Centro para el Estudio de Sistemas Marinos (CESIMAR-CONICET). Boulevard Brown 2915, C. P. U9120ACD, Puerto Madryn. Chubut, Argentina. E-mail: lebder@gmail.com (EBE).

5Longbow Lake. Storm Bay Road, 22-15. C. P. P0X 1H0. Ontario, Canadá. E-mail: dadiva47@gmail.com (LD-T).

6Comité de Atención a Fauna Silvestre. Calle río azul, C. P. 70989, Huatulco. Oaxaca, México. E-mail: chris.casillas@hotmail.com (CC-A).

*Corresponding author

The southern elephant seal (Mirounga leonina) has a circumpolar distribution in the southern hemisphere. However, recent observations have documented this species in several locations across the northern hemisphere. With the integration of citizen science, we report 3 new records of this species in México. Photographs, videos, and information on elephant seals were collected with the collaboration of citizens (fishermen and photographers) on the Gulf of California and the southern Mexican Pacific coast. Data regarding the date, time, geographic location, and general behavior of the elephant seal were obtained from these sightings. The species, sex, and age category of the pinnipeds were identified based on external morphological characteristics. Three sightings of different southern elephant seal individuals were recorded on the Pacific Ocean coasts of México. In February 2021, a juvenile male was observed in Bahías de Huatulco, Oaxaca. In May 2022, a subadult male was sighted in San Jorge Bay, Sonora. In February 2023, another subadult male was observed in the Gulf of Santa Clara, Sonora. We documented 3 extralimital sightings of the southern elephant seal, with one being this species' northernmost record in the Pacific Ocean. These records contribute to our understanding of the dispersal patterns of southern elephant seals and highlight the importance of citizen science in advancing knowledge of marine mammal distributions.

Key words: Climate change; dispersal; migration; pinniped; vagrant individual.

El elefante marino del sur (Mirounga leonina) tiene una distribución circumpolar en el hemisferio sur. Sin embargo, observaciones recientes han documentado esta especie en varios lugares del hemisferio norte. Con la integración de la ciencia ciudadana, se reportan 3 nuevos registros de esta especie en México. Se recopilaron fotografías, videos e información de elefantes marinos con la colaboración de ciudadanos (pescadores y fotógrafas) en el Golfo de California y la costa sur del Pacífico mexicano. De los avistamientos se obtuvo información sobre la fecha, hora, ubicación geográfica y comportamiento general del elefante marino. La especie, sexo y categoría de edad de los pinnípedos se identificaron con base en características morfológicas externas. Se registraron 3 avistamientos de individuos diferentes de elefante marino del sur en las costas del océano Pacifico de México. En febrero de 2021 se observó un macho juvenil en Bahías de Huatulco, Oaxaca. En mayo de 2022 se avistó un macho subadulto en la Bahía de San Jorge, Sonora. En febrero de 2023 se observó otro macho subadulto en el Golfo de Santa Clara, Sonora. Documentamos 3 avistamientos extralimitales del elefante marino del sur, uno de los cuales es el registro más septentrional de esta especie en el Océano Pacífico. Estos registros contribuyen a la comprensión de los patrones de dispersión de los elefantes marinos del sur y resaltan la importancia de la ciencia ciudadana para avanzar en el conocimiento de las distribuciones de los mamíferos marinos.

Palabras clave: Cambio climático; dispersión; individuos solitarios; migración; pinnípedos.

Citizen science in marine mammal monitoring and scientific research has experienced a notable increase in recent years. This growing trend highlights the significant contribution of citizen science to enhancing our understanding of marine mammal diversity and distribution (García-Cegarra et al. 2021; Adamantopoulou et al. 2022). Additionally, citizen science generates valuable data in remote and inaccessible areas that researchers have difficulty accessing, thus contributing to identifying existing threats to marine mammals (Curtis et al. 2021). Furthermore, citizen science has proven to be a relevant and reliable tool for monitoring species distribution and recording the presence of pinnipeds and other marine mammals in various regions worldwide (Sayer et al. 2019; Kelly et al. 2020).

Unusual records of live pinnipeds sighted beyond their previously known distribution range have increased in recent decades (Milmann et al. 2019; Bester et al. 2022; De Weerdt et al. 2024). México is home to 4 pinniped species: the California sea lion (Zalophus californianus), the Guadalupe fur seal (Arctocephalus townsendi), the northern elephant seal (Mirounga angustirostris), and the Pacific harbor seal (Phoca vitulina richardii) (Gallo-Reynoso et al. 2010; Schramm and Heckel 2021; Barba-Acuña et al. 2022). Additional records of various pinniped species from regions beyond their usual range have been observed along the shores of the Mexican Pacific. These species mentioned come from both the northern and southern hemispheres, including the Steller sea lion (Eumetopias jubatus; Gallo-Reynoso et al. 2020), South American fur seal (A. australis; Villegas-Zurita et al. 2016), Galapagos fur seal (A. galapagoensis; Aurioles-Gamboa et al. 2004; Tamayo-Millán et al. 2021), Galapagos sea lion (Z. wollebaeki; Elorriaga-Verplancken et al. 2022), South American sea lion (Otaria flavescens; Ceballos et al. 2010; Gallo-Reynoso et al. 2020), and Southern elephant seal (M. leonina; Elorriaga-Verplancken et al. 2020; Alava et al. 2022; Cerillo-Espinosa et al. 2023; Romero-Tenorio et al. 2023).

Elephant seals (M. leonina and M. angustirostris) are the largest phocids and exhibit the most remarkable sexual dimorphism of all marine mammals (Lewis and Eder 2021). These 2 large phocids have antipodal distributions. The range of the northern elephant seal (M. angustirostris) includes islands and coastal areas of California, United States, and Baja California, México (Lowry et al. 2014). However, the southern elephant seal (M. leonina) has a circumpolar distribution in the southern hemisphere, with most colonies primarily located on sub-Antarctic islands (Hindell et al. 2016). Additionally, there are established colonies on Península de Valdés, Argentina (Campagna and Lewis 1992), and emerging colonies on the coast of Chile (Acevedo et al. 2016; Capella et al. 2017; Sepúlveda et al. 2018; Cárcamo et al. 2019).

Elephant seals undertake long-distance migrations from their breeding grounds to their foraging areas (Lewis and Eder 2021; Robinson et al. 2012), generally exhibiting philopatry to their breeding grounds (Le Boeuf et al. 2019; Chua et al. 2022). Extralimital records beyond their typical distribution range indicate extensive dispersal capabilities (Lewis et al. 2006; Páez-Rosas et al. 2018). This study presents 3 new records of the southern elephant seal: 1 in the southern Mexican Pacific and 2 in the Gulf of California. These records were obtained through citizen science, with one representing the northernmost record for the species to date.

Photographs and videos of elephant seals were collected with the collaboration of fishermen and photographers along different coasts of México. These photos and videos were taken opportunistically and shared via social media to the first author of this manuscript. Collecting wildlife sightings and data through citizen science provides speed, data accuracy, and cost-effectiveness (Dickinson et al. 2012; Fulton et al. 2019; Monzón-Alvarado et al. 2020). Muñoz-Espinoza, a fisherman and participant in the biological monitoring group "Grupo Lobos," which monitors California sea lions (Zalophus californianus), ospreys (Pandion haliaetus), and other seabirds in San Jorge Bay since 2013, contacted the first author to provide a video and photographs of an individual observed in San Jorge Bay, Sonora. C. Casillas-Angón, a photographer, captured photographs of an individual on the Oaxaca coast. Additionally, the fisherman F. Pérez-Tapia and the photographer L. Dobbin-Turner photographed an individual in the Gulf of Santa Clara, Sonora. The photographers were contacted to obtain supplementary details about the records, such as the date, time of the sighting, exact geographic coordinates, and the behavior exhibited by the elephant seal. Additional photographs were requested, and we chose the best photograph from each of the 3 sightings to highlight the distinctive characteristics of the species and determine its sex and age category.

The taxonomic and sexual identification of the 3 elephant seals observed in Oaxaca and Sonora was determined by the authors of this manuscript. Four authors have conducted biological research with the northern elephant seal in México, and one author with the southern elephant seal in Argentina. For the species identification, we considered external morphological characteristics, the neck-to-head size ratio, and the size and shape of the proboscis (Alava et al. 2022; Romero-Tenorio et al. 2023). Compared to northern elephant seals of the same age class, the proboscis of the southern elephant seal is shorter and smaller (Galimberti et al. 2019; Lewis and Eder 2021). The phenology of M. leonina was also considered to categorize the molt stage of the individuals (Páez-Rosas et al. 2018; Lewis and Eder 2021).

Our results add 3 new sightings of southern elephant seals (Mirounga leonina) in the northern hemisphere, documented between 2021 and 2023 in the southern Mexican Pacific and the Gulf of California (Figure 1). The first southern elephant seal individual was observed and photographed by a citizen at Pescadores Beach, Tangolunda, Bahías de Huatulco, Oaxaca (15º 49' 24.9" N, 95º 57' 56.8" W), on February 3, 2021, at 11:00 hr. Based on the absence of a discernible gular shield, this individual was identified as a male juvenile, approximately 4 years old. The individual was determined to be a male by observing the umbilicus and the penile fold in the ventral area (Figure 2a). The individual was in molting stage, as evidenced by the pieces of old fur still attached to its skin (Figure 2a). This juvenile was observed conducting thermoregulatory behavior (defined by throwing sand on its body with its fore flippers; Figure 2b).

The second individual, identified as a subadult male (Figure 3a), was sighted by a fisherman during the biological monitoring activities of "Grupo Lobos" in Campodónico, San Jorge Bay, Sonora (31º 04' 16" N, 113º 06' 59.8" W) on May 6, 2022, at 13:00 hr. The individual was seen with no evidence of molting. On the monitoring outing the next day (May 7, around 08:00 hr), the individual was not observed at the location.

The third individual was photographed and recorded by a fisherman in the Gulf of Santa Clara (Sonora coast), located at the Upper tip of the Gulf of California, on February 24, 2023. Based on its body size and distinctive nose, it was identified as a subadult male. The significant lack of scarring on its neck suggests that it may not yet be an active breeder. It was observed at approximately 11:00 hr, roughly 8 km from the fishing community (31° 38' 42.8" N, 114° 25' 48.5" W). Later, at approximately 19:00 hr, the individual was observed 4 km further north (31° 39' 53.9" N, 114° 27' 20.8" W; F. Pérez-Tapia pers. comm., February 24, 2023). The individual was observed entering tidal sea ponds to thermoregulate. From February 25 to 27, the individual was no longer observed in the area. However, on February 28, it was sighted and photographed by a citizen further north (Figura 3b). It was considered the same individual due to a visible and distinct scar on the proboscis (Figure 3c).

Southern elephant seals exhibit congregations during the molting season (November through March) and the breeding season (August through November), maintaining relatively high site fidelity during their annual life cycle (Lewis and Eder 2021). The subadult male individual from the Gulf of Santa Clara, observed in February 2023, appeared to be in very good body condition, suggesting recent successful foraging trips. Its skin displayed a light yellowish-beige color characteristic of old fur (Lewis and Eder 2021), with minimal evidence of molting at the foreback hind flippers, suggesting it may have hauled out to initiate its annual molting. The subadult individual observed in San Jorge Bay in May 2022 was seen with no evidence of molting. This sighting occurred when subadult males of the species typically undertake their foraging trips post-molt, as the molting period for adult and subadult males occurs between January and March (Lewis et al. 2006; Lewis and Eder 2021). Juvenile and subadult males are regarded as broad vagrants by several authors (Lewis et al. 2006; Páez-Rosas et al. 2018; Lewis and Eder 2021).

The dispersal of vagrant individuals of M. leonina has been reported across a wide range of latitudes of the Atlantic, Indian, and Pacific Oceans (Lewis et al. 2006; Elorriaga-Verplancken et al. 2020; de Vos 2021; Lewis and Eder 2021). In the southern hemisphere of the Pacific Ocean, the dispersal of some individuals has been observed along the coasts of Chile (Cárcamo et al. 2019), Perú (Acevedo et al. 2016), and Ecuador (Alava and Carvajal 2005; Félix 2018; Rosero and Alava 2021), including the oceanic islands of Pascua, Juan Fernández, and Galápagos (Aguayo-Lobo et al. 1995; Acevedo et al. 2016). Additionally, there are records of the southern elephant seal in the northern hemisphere of the Pacific Ocean. They have been recorded in Ecuador (Páez-Rosas et al. 2018), Colombia (Ávila et al. 2021), Panamá (Redwood and Félix 2018), El Salvador (Alava et al. 2022; López et al. 2022), Guatemala (Alava et al. 2022), and México (Elorriaga-Verplancken et al. 2020; Alava et al. 2022; Cerillo-Espinosa et al. 2023; Romero-Tenorio et al. 2023).

The most recent reports of extralimital records of the southern elephant seal in the northern region were documented at 2 locations in Baja California Sur, México (Elorriaga-Verplancken et al. 2020; Alava et al. 2022). Our observation in the Gulf of Santa Clara (Sonora) extends approximately 600 to 1,000 km north of these locations, making it the current northernmost record for the southern elephant seal in the Pacific Ocean. The southernmost breeding colony of this species in the Pacific Ocean was recorded in Almirante Montt Gulf, Chile (Capella et al. 2017). The straight-line distance from that colony to the recorded site in the Gulf of Santa Clara is approximately 10,100 km, suggesting that the subadult male recorded in this region could have traveled this distance. This could represent one of the most extended transhemispheric dispersal movements recorded for a pinniped (Lewis and Eder 2021; Sousa-Lima et al. 2022), but significant research is required to prove this hypothesis. Changes in the marine environment can influence the movements and feeding strategies of southern elephant seals, potentially driving long-range migrations and displacement of individuals to optimize foraging efficiency in response to shifting environmental conditions (Oosthuizen et al. 2011; Ávila et al. 2021; Chua et al. 2022).

The northward expansion and extralimital dispersal of M. leonina in the Pacific Ocean have been attributed to environmental changes, particularly in seawater temperature linked to climatic-oceanographic variations associated with "La Niña" cold event in the southeast Pacific (Páez-Rosas et al. 2018; Redwood and Félix 2018; Ávila et al. 2021). Our sightings in February 2021 in Oaxaca, and in May 2022 and February 2023 in Sonora also coincide with a La Niña event. However, extralimital records have been observed in non-La Niña conditions, such as September 2019 (Elorriaga-Verplancken et al. 2020). Other factors, including marine currents (López et al. 2022) and environmental and climate change factors (e.g., ocean heat waves, changes in primary productivity, increased sea surface temperature, and prey availability), may influence the extralimital dispersal of M. leonina and the plausible exploitation of potentially suitable habitat niches (Alava et al. 2022). Additionally, the increase in specific southern elephant seal populations in circumpolar regions cannot be disregarded as a factor influencing extralimital dispersal, especially among non-adult individuals, due to the potential for new feeding areas in emerging environmental niches (Alava et al. 2022). Monitoring these individuals through GPS/satellite tracking and tagging could help us understand their movements, colonies of origin, and habitat utilization during changing marine environmental conditions (Lewis et al. 2006; Páez-Rosas et al. 2018).

Extralimital records of marine species outside their usual distribution range, obtained through citizen science, provide valuable insights into ecosystem changes and the recovery of previously exploited species (Adamantopoulou et al. 2022; Cranswick et al. 2022). Combining data generated with citizen science with expert analyses and interpretations in marine mammal research is increasingly common and can expand sources of knowledge, generate accurate data, and foster collaboration (Lodi and Tardin 2018; Wood et al. 2021). These extralimital records of M. leonina in México contribute significantly to our understanding of the dispersal behavior of this pinniped species in the Pacific Ocean. They highlight the potential of citizen science in fostering collaboration to enhance our knowledge of the distribution of marine mammals and other top predators, which may be considered sentinels of the ocean in the context of progressing climate change.

Acknowledgements

Special thanks to "Grupo Lobos" of the Campodónico community for their support in monitoring wildlife on the northeastern coast of the Gulf of California. The authors acknowledge L. Armenta-Méndez from CIAD and ECOGRANDE A. C. for providing training on monitoring ospreys to "Grupo Lobos". Thanks to CONANP and CEDO for additional monitoring training provided to "Grupo Lobos". We thank F. Pérez-Tapia for sharing photographs and videos of the subadult male from the Gulf of Santa Clara for better identification and the reviewers whose comments improved this note. M. E. Sánchez-Salazar edited the English manuscript.

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Associated editor: Nicté Ordóñez Garza.

Submitted: March 9, 2024; Reviewed: July 16, 2024.

Accepted: August 6, 2024; Published on line: August 21, 2024.